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Activity Number: 487
Type: Contributed
Date/Time: Wednesday, August 7, 2013 : 8:30 AM to 10:20 AM
Sponsor: Biopharmaceutical Section
Abstract - #309381
Title: Two-Threshold Model for Immunological Correlates of Protection
Author(s): Hongbo Lin*+ and Fabrice Bailleux and Xuan Chen and Kamal Desai and Andrew Dunning
Companies: and Sanofi Pasteur and Sanofi Pasteur and Imperial College and Sanofi Pasteur
Keywords: Correlation of Protection ; Chang-Kohberger Method ; a:b Model ; Two-threshold Method
Abstract:

Immunological assays measure characteristics of the immune system, such as antibody concentrations, that are believed to be associated with protection from disease. Thresholds of the assay measurements are routinely relied upon in vaccine research and public health immunization policy to differentiate protected from susceptible individuals. The Chang-Kohberger method and a:b model have been used to identify the threshold. Both these methods are based on the assumption that the threshold is the same for the vaccine group and the non-vaccine group. However, this assumption is unlikely to be valid in reality. We develop a model which allows separate thresholds for the vaccine group and non-vaccine group by extending the a:b model and using the Chang-Kohberger equation as a constraint to discover the relationship between the two thresholds to determine the pairs of threshold candidates for the two groups. The pair that maximizes the profile likelihood is selected. In addition, a test for whether the two thresholds are the same and a method for confidence regions for them will be proposed.


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